Prostaglandin D2 (PGD2) is a metabolic product of arachidonic acid through PGG2 and PGH2, and known to have various potent physiological activities. For example, in non-patent literature 1 it is described that PGD2 is involved in sleeping and secretion of hormones in central nervous system, and in inhibiting activity of platelet aggregation, contraction of bronchial smooth muscle, vasodilation and constriction of a blood vessel etc. in peripheral system.
Moreover, PGD2 is considered to be involved in forming pathological condition of an allergic disease such as bronchial asthma since it is a major metabolic product of arachidonic acid produced from a mast cell, and has a potent bronchoconstricting effect, causing an increase of vascular permeability and migration of inflammatory cell such as eosinophils.
A DP receptor (also called DP1 receptor) or CRTH2 receptor (also called DP2 receptor) is known as a receptor of PGD2. A phenylacetic acid derivative having a DP receptor antagonistic activity is disclosed in Patent literature 1, a sulfonamide derivative having a CRTH2 receptor antagonistic activity is disclosed in Patent literature 2 and a phenoxyacetic acid derivative having a CRTH2 receptor antagonistic activity is disclosed in Patent literatures 3-6.
Also, sulfonamide derivatives having an activity other than the PGD2 receptor antagonistic activity are disclosed in Patent literatures 7-12 and Non-patent literatures 2-3.    Patent literature 1: WO 2003/078409 Pamphlet    Patent literature 2: WO 2003/097598 Pamphlet    Patent literature 3: WO 2004/089884 Pamphlet    Patent literature 4: WO 2004/089885 Pamphlet    Patent literature 5: WO 2005/106302 Pamphlet    Patent literature 6: WO 2006/056752 Pamphlet    Patent literature 7: WO 1993/012086 Pamphlet    Patent literature 8: WO 2004/073606 Pamphlet    Patent literature 9: EP 76996A Pamphlet    Patent literature 10: WO 2006/059801 Pamphlet    Patent literature 11: JP 3-275678A Pamphlet    Patent literature 12: JP 3-275679A Pamphlet    Non patent literature 1: Pharmacol. Rev., 1994, Vol. 46, p. 205-22    Non patent literature 2: Chem. 86 Pharm. Bull., 1994, Vol. 42, p. 521-29    Non patent literature 3: Chem. & Pharm. Bull., 2000, Vol. 48, p. 1978-85